Hitherto, dental composite resins or dental glass ionomer cements have been used for filling restoration of fine deficient portions of tooth, core construction after the toot canal treatment, and the like. Also, materials having a great fluidity imparted to dental composite resins or dental glass ionomer cements, which are called as a dental sealant, have been used for sealing of pit and fissure for the purpose of preventing a tooth from occurrence of dental caries.
The dental composite resins have such features that they have relatively high mechanical characteristics and that they have a color tone close to a tooth and are particularly suitable for filling restoration or core construction.
On the other hand, although the dental glass ionomer cements are inferior to the dental composite resins with respect to the mechanical characteristics and esthetics such as color tone or surface smoothness, they have such a feature that they release a fluorine ion. The released fluorine ion replaces a hydroxyl group in an apatite in the dental structure to increase the acid resistance of the apatite, leading to prevention of dental caries from occurrence or making it hard to disease secondary caries. Accordingly, the dental glass ionomer cements are particularly suitable for filling restoration or sealing of pit and fissure.
In recent years, the development of materials having features of both dental composite resin and a dental glass ionomer cement in combination is being achieved. For example, resin-reinforced glass ionomer cements are ones comprising a dental glass ionomer cement having unsaturated double bond-containing monomer compounded therewith. However, the resin-reinforced glass ionomer cements have not enough mechanical characteristics compared with the dental composite resins. Also, in order to provide the dental composite resin with an ability for releasing a fluorine ion, a product comprising a dental composite resin having a quaternary ammonium salt of hydrofluoric acid compounded therewith, which is called as a compomer composite, is known. However, the stability of this material in an oral cavity is low due to the compounding of a quaternary ammonium salt of hydrofluoric acid. Accordingly, it can not be said yet that the development of materials having respective features of a dental composite resin and of a dental glass ionomer cement in combination is sufficient, and the materials having clinically satisfactory properties have not been developed yet.